In cooking and shopping for ingredients, the differences between flours and flour products can be a confusing part of the process. Durum wheat, for instance, provides both semolina and durum flours and is used in products ranging from baked breads to enriched pastas. Getting the right flour or grain for your next culinary project can be a bit easier if you understand the difference between semolina and durum flour.
Both semolina and durum flour are products rendered from milled durum wheat. The endosperm—the nutrients surrounding the wheat seeds—is separated from the grain through the milling process resulting in coarsely-ground flour known as semolina. The texture of semolina is heavier—like hard bread crumbs—and is more coarse than most milled flours. Durum flour is the fine ground powder left over from the milling process and also a product of semolina that is ground further. Durum flour is much finer than semolina and is a yellow-hued powder that resembles more traditional baking flours.
Semolina and durum flour are both high in proteins and gluten, a wheat-specific protein that people suffering from celiac disease cannot eat. These proteins make the flours very pliable in dough form and allow them to hold up well under heated conditions. In semolina, the coarse texture of the flour works like a composite material, holding the pasta dough together and strengthening it when heated. Durum flour, with its more delicately ground texture, creates a softer dough that is forced through pasta makers more easily and bends or curls when cooked.
Semolina and durum flour are traditionally used in pastas, noodles and even some breads that need to impart a coarse, hard texture. Semolina's coarse and grainy texture makes it usable for hard pastas that maintain shapes under heat. Rotini, farfale and macaroni all use semolina's shape-retention properties to give their pasta pieces distinct shapes. Durum flour is used in softer noodle products like spaghetti and lasagna so that the pasta becomes softer and more pliable when cooked. Durum flour's fine grain texture also lends itself well to baking, offering hard wheat textures to breads and doughs.